This invention relates to tie replacing systems, and more particularly to a fully automatic tie replacing system which is both economical in use and capable of very high speed operations.
At the present time there is renewed interest in the use of railroads for high speed inter-urban mass transportation, particularly in the eastern and northern sections of the country where the cities have literally grown together. Federal regulations have established track maintenance standards which, for purposes of safety, limit the speed of trains in accordance with track conditions. Therefore, in order to provide high speed railroad transportation, be it inter-urban in nature or cross country, it is necessary that the various railroad tracks traversing the United States be generally upgraded. This effort must of course be carried on in addition to normal maintenance of way activities.
There are, of course many factors involved in upgrading a railroad track. For example, it is now considered desirable to connect adjacent rails of a railroad track with welded joints rather than by means of conventional bolted joints. This is advantageous not only in providing a quieter and smoother ride, but also in reducing damage to rolling stock caused by vibrations and shock. It is also often necessary to renew and/or replace the roadbed which supports the railroad track, particularly the ballast. Finally, the ties which support the rails of the track on the roadbed must be replaced on a periodic basis. The average wooden railroad tie should be replaced after about 30 years of service.
Heretofore the replacement of ties in a railroad track has typically involved a large number of independent, time consuming steps. First, the ties to be replaced are identified, the rail anchors are removed, and the ties are unspiked. Since the tie plates which support the rails on the ties are often buried in the older ties to a greater or lesser degree, and since raising the track to remove the old tie is not desirable for several reasons, it is often necessary to employ a tie saw to cut the old ties into three pieces. A tie crane is then employed to remove the pieces and to position them adjacent the railroad track.
A second tie crane is typically employed to position a new tie for insertion beneath the rails of the track. Various semi-automatic mechanisms have heretofore been designed, any of which may be employed to push or pull the new ties onto the rails. Finally, the ballast structure around the new ties is restored, and the spikes and the rail anchors are replaced,
The present invention comprises a tie replacing system incorporating numerous advantages over the foregoing procedure. In accordance with the broader aspects of the invention, any portions of a worn tie which extend above the tie plates are first removed, and the tie plates are simultaneously gripped and thereby maintained in engagement with the under surfaces of the rails. Thereafter a tie pushing-tie pulling mechanism supported on an articulated arm is forced beneath the rails, whereby the worn tie is pushed out from under the rails. The worn tie is thrown clear of the track structure, and the new tie is delivered to the tie pushing-tie pulling mechanism. The articulated arm is then actuated to withdraw the tie pushing-tie pulling mechanism from beneath the rails, whereby the new tie is pulled into the position previously occupied by the worn tie. By this means the worn tie is replaced in a single operation which is much faster and much less expensive than prior tie replacing processes.
In accordance with more specific aspects of the invention, an anchor arm is engaged with the track supporting structure on the oposite side of the track from the point of entry of the tie pushing-tie pulling mechanism. By this means the reaction force which is generated as the old tie is pushed out from under the rails is absorbed in the track supporting structure, and is not applied to the rails per se. The tie pushing-tie pulling mechanism includes a vibrating mechanism which aids in the movement of the worn and replacement ties out of and into the roadbed, respectively, and a pair of opposed jaws which are utilized to grip the new tie as it is pulled into position. The tie pushing-tie pulling mechanism also includes a scarifyer which adapts the roadbed to receive the new tie.
The portions of the worn tie which project above the tie plates are preferably removed by a tie biter-tie plate holder assembly. As the old worn tie is pushed out from under the rails, the new tie is simultaneously positioned above the point at which the worn tie is removed from the track structure. Thereafter, a tie feeder operates in conjunction with the force of gravity to rapidly move the replacement tie into engagement with the jaws of the tie pushing-tie pulling mechanism. The tie biter-tie plate holder assembly and the tie feeder also guide the replacement tie during the tie pulling operation.